On Tuesday, the former Glendale Community College player appeared to justify the move with a spotless inning of relief against the Cincinnati Reds in his season debut. The Pirates would lose the game, 8-1, but perhaps saw a glimpse of the steady veteran play they were looking for when they promoted Slaten to join Tony Watson as the team's only left-handers out of the bullpen. Slaten retired the Reds' Nos. 2-4 hitters, Drew Stubbs, lefty slugger Joey Votto and Brandon Phillips in order to keep the Pirates within four runs in the fourth.

Prior to his call up, Slaten was 2-0 with eight saves and a 0.36 earned-run average in 20 games with Indianapolis (25 1/3 innings) this season.

"He's earned this opportunity. He finally got in shape in early April," Pirates Manager Clint Hurdle told mlb.com of Slaten, who had a 9.00 ERA in six spring training appearances with the club. "The last month, his bundle of work has been very clean. We felt he deserved this opportunity in [Juan] Cruz's absence."

Pittsburgh (24-25 for third place in the National League West) made room for Slaten by placing reliever Juan Cruz on the restricted list.

Slaten, who broke into the big leagues with the Arizona Diamondbacks in 2006, spent the last two seasons with the Washington Nationals before signing a minor league contract with the Pirates in the offseason.